US6169531B1 - Liquid-crystal control circuit display device with selection signal - Google Patents

Liquid-crystal control circuit display device with selection signal Download PDF

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US6169531B1
US6169531B1 US08/795,122 US79512297A US6169531B1 US 6169531 B1 US6169531 B1 US 6169531B1 US 79512297 A US79512297 A US 79512297A US 6169531 B1 US6169531 B1 US 6169531B1
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display device
crystal material
selection
electrodes
row
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Antonius G. H. Verhulst
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US Philips Corp
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US Philips Corp
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • G09G3/3651—Control of matrices with row and column drivers using an active matrix using multistable liquid crystals, e.g. ferroelectric liquid crystals
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • G09G3/3659—Control of matrices with row and column drivers using an active matrix the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0202—Addressing of scan or signal lines
    • G09G2310/0205—Simultaneous scanning of several lines in flat panels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0243—Details of the generation of driving signals
    • G09G2310/0251—Precharge or discharge of pixel before applying new pixel voltage
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/06—Details of flat display driving waveforms
    • G09G2310/061—Details of flat display driving waveforms for resetting or blanking

Definitions

  • the invention relates to a display device comprising a number of display elements, which are arranged in rows and columns in accordance with a matrix, and comprising, between a first substrate and a second substrate, a liquid-crystal material which belongs to the group of smectic liquid-crystal materials, which include ferroelectric liquid-crystal material with deformable helix, ferroelectric liquid-crystal material with twisted smectic structure, monostable ferroelectric liquid-crystal material, electroclinic smectic A liquid-crystal material and anti-ferroelectric liquid-crystal material, and comprising a group of row electrodes and a group of column electrodes, each pixel including, on at least one substrate, a picture electrode which is connected to a column electrode or row electrode via an active switching element, and said display device comprising means for applying selection voltages to the row electrodes and data voltages to the column electrodes.
  • smectic liquid-crystal materials which include ferroelectric liquid-c
  • Such display devices can be used as video displays, but also, for example, in datagraphic monitors or as view finders.
  • a ferroelectric liquid-crystal material with a deformed helix is to be understood to mean a ferroelectric liquid-crystal material with a natural helix whose pitch is smaller than the wavelength of visible light (up to approximately 400 nm).
  • An electric field which extends perpendicularly to the axis of the helix causes deformation of said helix, which results in rotation of the optical axis.
  • crossed polarizers one of which extends parallel to the axis of the helix, the transmission increases for both positive and negative fields.
  • the ferroelectric liquid-crystal material with a deformed helix exhibits a high degree of polarization in the fully driven state. If they are provided between a polarizer and an analyzer, the above-mentioned materials have another characteristic in common, namely that they can switch between substantially transparent and substantially opaque if the polarizer and the analyzer are at a specific angle with respect to each other, while intermediate levels of transparency (grey levels) can also be realized.
  • a display device of the type mentioned hereinabove is described in “A Full-Color DHF-AMLCD with Wide Viewing Angle” in SID 94 DIGEST pp. 430-433.
  • DHFLC material Deformed Helix Ferroelectric Liquid Crystal
  • SSFLC devices Surface Stabilized Ferroelectric Liquid Crystal
  • the customary pulse duration of drive pulses (which, in practice, is comparable to a pulse duration of the order of, for example, half the row-selection time of the drive system, which amounts, for example, in TV systems to 64 ⁇ sec.) is too short to supply the polarization current. Transient phenomena occur which may extend over a plurality of frame or field times.
  • Yet another example is the anti-ferroelectric liquid-crystal effect, as described, for example, in Asia Display '95 pp. 61-64.
  • PAL 50 Hz
  • Another object of the invention is to provide a device in which little, if any, “after image” occurs.
  • a display device in accordance with the invention is characterized in that the display device comprises a control circuit which, during a first part of a line-selection time, provides a first number of successive row electrodes with a selection signal for the purpose of reset and which, during a corresponding part of a subsequent line-selection time, provides a second number of successive row electrodes, yet shifted by at least one line position, with a selection signal for the purpose of reset and which, during another part of a line-selection time, provides one or two row electrodes with a selection signal for the purpose of writing data and which provides the column electrodes with data signals.
  • “successive row electrodes” can also be understood to mean a number of row electrodes at one extreme edge (for example the last row electrodes) together with a number of row electrodes at the other extreme edge (for example the first row electrodes).
  • the even fields and the odd fields, for example, of a television picture are partly interlaced.
  • the type of application determines whether selection offset by one or two line positions takes place and whether, during other parts of a line-selection time, one or two row electrodes are provided with a selection signal for writing data.
  • the invention is based on the recognition that, unlike known (ferroelectric) liquid-crystal display devices, upon application of a voltage across a pixel, the spontaneous polarization of DHFLC materials (and the other materials mentioned hereinabove) plays such an important part that either it requires such a long time that the display device as a whole becomes too slow or the pixel does not always receive the desired charge and the associated transmission value.
  • it is proposed to bring a row of display elements to an extreme optical transmission state by means of an auxiliary voltage (reset), prior to selection, but also in this case the pixel does not always receive the desired charge owing to the great importance of the polarization, so that incomplete reset occurs.
  • the “memory effect” is eliminated at least substantially by providing the pixels in a first number of successive rows with a reset signal during a first part of the line-selection time, repeating this in subsequent line-selection times for a second number of successive rows, yet shifted by at least one line position, and providing the column electrodes with data signals during every second part of the line-selection time.
  • the joint effect of the reset signals presented during the first parts of the number of successive line-selection times is sufficient, if the numbers are suitably chosen, to achieve a complete reset.
  • resetting causes the pixels to switch to an opaque state, which results in a better contrast.
  • each pixel can be provided with an additional capacitor.
  • the charge stored on the additional capacitor during the selection period (which can be much shorter now) also determines the charge across the pixel (and hence the polarization).
  • FIG. 1 schematically shows an electrical equivalent circuit diagram of a part of a display device in accordance with the invention
  • FIG. 2 schematically shows a cross-section of the device shown in FIG. 1,
  • FIG. 3 schematically shows the position of the polarizers relative to the helix (FIG. 3 a ) and a transmission voltage characteristic (FIG. 3 b ) of a device in accordance with the invention
  • FIG. 4 schematically shows a number of different voltage curves and the associated polarization and transmission curves for the device shown in FIG. 1, which is operated in accordance with the invention.
  • FIG. 1 schematically shows an electrical equivalent circuit diagram of a part of a display device 1 .
  • This device includes a matrix of pixels 2 which are arranged in rows and columns.
  • the pixels 2 are connected to column electrodes or data electrodes 4 by means of three-pole switches, in this example TFT transistors 3 .
  • a row of pixels is selected via row or selection electrodes 5 which select the relevant row via the gate electrodes of the TFTs.
  • the row electrodes 5 are successively selected by means of a row-drive circuit 6 .
  • Incoming data signals or (video) information 7 are processed in a processing/control unit 8 and stored in a data register 9 .
  • the voltages provided by the data register 9 cover a voltage range which is sufficient to set the desired range of grey levels.
  • Pixels 2 in this case represented by capacitors 2 , are charged positively or negatively via the TFTs 3 as a result of the fact that, during selection, the picture electrodes 13 take over the voltage from the column electrodes.
  • the picture electrodes 14 form a common counter electrode, which is referenced 16 . Synchronization of said picture electrodes takes place via control lines 17 .
  • each pixel may also be provided with an auxiliary capacitor 33 .
  • Said auxiliary capacitors 33 (shown for only one column in FIG. 1) reduce the voltage loss across the pixels.
  • Said auxiliary capacitors have a capacitance value which is approximately 10 times (5 to 20 times) as high as that of a pixel.
  • FIG. 2 is a schematic, cross-sectional view of the device shown in FIG. 1 .
  • a first substrate 18 there are row or selection electrodes (not shown), as well as column or data electrodes 4 and picture electrodes 13 , which are made, in this example, of a transparent, conductive material such as indium-tin oxide, which electrodes are connected to the column electrodes 4 via the TFTs 3 by means of (schematically shown) connections 19 .
  • the device further comprises a first polarizer 20 and a second polarizer or analyzer 21 whose polarization axes intersect at right angles.
  • FIG. 3 schematically shows a transmission/voltage characteristic (FIG. 3 b ) of a cell in such a device, in which, due to the absence of the electric field, the axis of the helix (and hence the optical axis 28 ) of the DHFLC material is chosen to extend parallel to one of the polarizers (see FIG. 3 a ), the so-called symmetric mode.
  • the molecules try to direct their spontaneous polarization towards the associated field, which leads, between crossed polarizers with the axis of the helix extending parallel to one of the polarizers, to a transmission/voltage characteristic which exhibits an increase in transmission for positive and negative voltages as the voltage increases (FIG.
  • the invention can also be applied in the so-called asymmetric mode in which the crossed polarizers are rotated relative to the substrates in such a manner that the optical axis of the helix of the DHFLC material coincides in the driven state with one of the directions of polarization.
  • FIG. 4 a schematically shows the voltage variation on a number of row electrodes 5 of the device shown in FIGS. 1, 2
  • FIG. 4 b shows the voltage variation on a random column electrode 4 .
  • a pulse 41 for the purpose of reset is presented to row n, while the voltage on the column electrode is, in this example, approximately 0 volt.
  • the row n is not selected, while the voltage on the column electrode is determined by the information which is written on a row which is not shown.
  • the values of t l , t r and t w are chosen to be such that t r +t w ⁇ t l .
  • the data register 9 is designed in such a manner that it provides the column electrodes, during the first part t r of the row-selection period t l , with a voltage of approximately 0 volt and, during the second part t w of the relevant line time t l , with the data voltages (column voltages), indicated as pulses 43 , intended for the selected row.
  • the counter electrode 16 has a voltage of approximately 0 volt.
  • the row-drive circuit provides the row n with selection pulses 41 for the purpose of reset and, in a subsequent (or a later) line time during the second part of the line time, with a selection pulse 42 for writing.
  • the last selection pulse 41 for the purpose of reset in row n and the selection pulse 42 for the purpose of writing, which are presented in different line times in FIG. 4 a may take place within one line time, if necessary.
  • the pulse 44 on the relevant column electrode 4 defines the voltage across the pixel selected in row n (FIG. 4 c ) and the associated transmission (FIG. 4 d ).
  • a striking feature in this connection is that in a number (in this case 8) of successive line times a complete reset (pixel voltage 0 volt and zero transmission) is achieved via a number of intermediate values.
  • the charge supplies a polarization current in the same row selection time, which current gives rise to the voltage curve 46 as shown in FIG. 4 c .
  • the reset pulse brings about a further reduction of the voltage amplitude until after (in this example) 8 row selection times a complete reset has taken place and the voltage determined by pulse 44 on the relevant column electrode 4 is written across the pixel selected in row n.
  • complete reset is achieved in a period of time which is much shorter than the actual field time or frame time.
  • a pixel receives the desired voltage (and transmission value), so that aftereffects do not occur.
  • the cell of the device shown in FIGS. 1, 2 is preferably driven with voltages of opposite sign. Consequently, prior to reset, the voltage across the selected pixel is of opposite sign to the voltage after writing. For the rows n+1, n+2, . . . the same pulse pattern is applied to the row electrodes as to the row n, yet shifted by one row selection time.
  • the number of pulses necessary for reset is also governed by the liquid-crystal material used and by the utilization, or not, of an auxiliary capacitor 33 , and it can be influenced by varying the duration of these pulses.
  • both reflective and transmissive display devices can be used.
  • the number of row electrodes which is provided with a reset pulse during one line time may vary, even within one display device, for example as a result of transient effects, or by commencing writing a new image in the case of “double row drive” or, for example, because a slightly longer reset action is locally necessary.
  • a first part of the line time can be used for selection for the purpose of writing, while during the second part of the line time a signal for the purpose of reset is continuously being energized.
  • the voltage of a counter electrode situated on the second substrate can alternate every field time with respect to an average voltage.
  • the drive circuit advantageously applies a voltage to the column electrodes, during the provision of a selection signal for reset, which voltage is substantially equal to that of the counter electrode.
  • the invention makes it possible to eliminate the memory effect in Deformed Helix Ferroelectric liquid-crystal display devices and liquid-crystal display devices based on similar materials (high polarization in the fully driven state), in particular in video applications, by presenting reset pulses in successive row selection times during a part of these times (for example in matrix displays based on TFTs), so that the polarization within a cell is always reduced to zero and, after selection for writing data, switches to the correct value.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
US08/795,122 1996-02-22 1997-02-07 Liquid-crystal control circuit display device with selection signal Expired - Fee Related US6169531B1 (en)

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EP (1) EP0823110A1 (ja)
JP (1) JPH11504732A (ja)
KR (1) KR19990008127A (ja)
WO (1) WO1997031362A1 (ja)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002061724A2 (en) * 2001-02-02 2002-08-08 Koninklijke Philips Electronics N.V. Display device
CN1302451C (zh) * 2002-03-07 2007-02-28 株式会社日立制作所 显示装置及其驱动方法
US20080165120A1 (en) * 2004-12-06 2008-07-10 Koninklijke Philips Electronics, N.V. Passive Matrix Electrophoretic Display with Reset

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US6323850B1 (en) * 1998-04-30 2001-11-27 Canon Kabushiki Kaisha Driving method for liquid crystal device
WO2000038158A1 (fr) * 1998-12-18 2000-06-29 Samuil Leibovich Gorelik Tableau d'affichage d'informations
JP3556150B2 (ja) * 1999-06-15 2004-08-18 シャープ株式会社 液晶表示方法および液晶表示装置
JP3486599B2 (ja) * 2000-03-31 2004-01-13 キヤノン株式会社 液晶素子の駆動方法
KR100367015B1 (ko) * 2000-12-29 2003-01-09 엘지.필립스 엘시디 주식회사 액정 표시장치의 구동방법
KR100367014B1 (ko) * 2000-12-29 2003-01-09 엘지.필립스 엘시디 주식회사 액정 표시장치 및 그 구동방법
JP2004070293A (ja) * 2002-06-12 2004-03-04 Seiko Epson Corp 電子装置、電子装置の駆動方法及び電子機器
JP4850850B2 (ja) * 2006-01-16 2012-01-11 富士通株式会社 表示素子の駆動方法、表示素子および電子端末

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002061724A2 (en) * 2001-02-02 2002-08-08 Koninklijke Philips Electronics N.V. Display device
WO2002061724A3 (en) * 2001-02-02 2003-11-06 Koninkl Philips Electronics Nv Display device
CN1302451C (zh) * 2002-03-07 2007-02-28 株式会社日立制作所 显示装置及其驱动方法
US20080165120A1 (en) * 2004-12-06 2008-07-10 Koninklijke Philips Electronics, N.V. Passive Matrix Electrophoretic Display with Reset

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WO1997031362A1 (en) 1997-08-28
EP0823110A1 (en) 1998-02-11
KR19990008127A (ko) 1999-01-25

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